Parallel Vertical Turbine Pump with Dismilar Impeller

[sinenhlanhla]

Hi,

We are having a challenge in the high lift pump station for the water treatment plant. 3 small pumps and 2 bigger pumps (vertical turbine pumps).

Pumps are operated as follow: 1 bigger pump (720mm impeller) and 3smaller pumps ( pump 01 365mm and pum02 & 03 are 376mm four-stage)

Most of the pump failure occurred on pump 02, thrust bearing collapsing most likely the cause of the pump failure and result in pump bottoming out and seizing up.

I want to conduct a study of why pump 02 always fails. Please advise.

 

[JJPellin]

Draw all of the pump curves for the group of running pumps on one plot. Determine the total differential head for the group of pumps based on the suction and discharge pressures. Recall, that if they are truly running in parallel, they all have the same suction pressure and the same discharge pressure. Draw a straight horizontal line through the group of pump curves based on the total head. Where that horizontal line crosses each pump curve, that is where that pump is running. Where is each pump running relative to its best efficiency point?

Here is a curve showing pumps we run in parallel on a cooling tower. We run two of the smaller capacity pumps and one of the larger. They run very well together despite being very different curves. We run them at about 125 feet TDH and all pumps are happy.

Johnny Pellin

 

[LittleInch]

Well from your pump curve as JJ says, you look as though pumps 2 and 3 will be running about 80% more fluid than pump 1.

So pump 2 is possibly running on the far right hand side of the curve, with greater flow, more vibration, high NPSHR.

They look like mixed flow pumps?

But head will probably be being set by the big pump.

your option is to maybe trim the impellers to all be 365?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

Send curve for the big pump -


It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[sinenhlanhla]

here, is the pump curve for a bigger pump

 

[Artisi]

What is the operating discharge pressure?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)